Close to three in five cities worldwide with at least 500,000 inhabitants are at high risk of a natural disaster, cautions UN DESA in its latest data booklet, The World’s Cities in 2018. Collectively, these cities are home to 1.4 billion people or around one third of the world’s urban population.

Issued ahead of the 31 October World Cities Day, the booklet found that 679 of the 1,146 cities with a population of at least half a million people, were vulnerable to either cyclones, floods, droughts, earthquakes, landslides or volcanic eruptions – or a combination of those.

Some large cities are exposed to as many as four or five different types of natural disasters. These include such large urban centres as Manila, Tokyo, Santiago and Guatemala City, the capitals of the Philippines, Japan, Chile and Guatemala respectively. Megacities of more than 10 million inhabitants are more exposed, with only three of them – Moscow (Russian Federation), Cairo (Egypt) and Kinshasa (Democratic Republic of the Congo) – deemed to be at low or at no risk of the six types of disasters analyzed by the study.

“Urban areas produce around 70 to 80 per cent of the world’s economic output and are home to 55 per cent of our population,” said UN DESA’s Danan Gu, lead author behind the study. “Such a concentration of people and economic activity means that natural disasters could be potentially costlier and more lethal if they hit cities.”

“Yet we still do not know enough about the exposure of the world’s urban populations to natural hazards, environmental degradation, and climate change,” he added. “With this study, we tried to learn more about cities’ vulnerability to natural disasters, including to mortality and economic loss.”

The theme of this year’s World Cities Day, Building Sustainable and Resilient Cities, highlights the need for cities to be able to absorb the impact of hazards, protect and preserve human life and limit damage and destruction while continuing to provide infrastructure and services after a crisis.

A recent report by the UN Office for Disaster Risk Reduction (UNISDR) found that natural disasters have killed 1.3 million people over the last 20 years and left a further 4.4 billion injured, homeless or in need of emergency assistance.

“This puts a big emphasis on the need to […] make sure that we curb greenhouse gas emissions,” said Ricardo Mena, responsible for supporting and monitoring the Sendai Framework implementation at UNISDR.

“Better preparedness, good governance and good infrastructure are also crucial steps to reduce the risk of life loss and economic loss in cities,” added UN DESA’s Danan Gu. Since these are easier to come by in developed countries, it is the less developed regions that are worst hit by disasters.

According to the UNISDR report, in the last 20 years, only one officially high-income territory – Puerto Rico – has featured in a league table of the top 10 economic losses as a percentage of gross domestic product (GDP). The UN DESA study found that while cities in developing countries have a relatively lower exposure to economic losses from natural disasters, they are more likely to be located in high mortality risk areas.